Charge plate fabrication technique

ABSTRACT

A charge plate and a method for fabricating a charge plate for an ink jet printhead includes the steps of removing portions of conductive material from a dimensionally stable substrate with a coating of conductive material to form at least a first and second electrode on a first face with a first space between the first and second electrodes, removing portions of conductive material from the dimensionally stable substrate with a coating of conductive material to form a first electrode extension which engages the first electrode on the conductive charging face, and a second electrode extension which engages the second electrode on the conductive charging face, whereby the first and second electrode extensions are electrically isolated from each other, additionally forming a first space between the electrode extensions, which connects with the first space between the electrode extensions.

FIELD OF THE INVENTION

The present embodiments relate to a method for making a charge plate foruse on ink jet printheads having drop generators, orifice plates andcharge plates.

The present embodiments relate to the charge plates used in ink jetprintheads that comprise drop generators, orifice plates forming a jetarray and a charge plate disposed opposite the charge plate.

BACKGROUND OF THE INVENTION

Current charge plate fabrication techniques are limited in the number oflines and spaces that can fit in a linear dimension. For example,current charge plates are typically made with 300-lines per inchresolution. Although higher resolutions can be achieved with thesetechniques, the higher resolutions come at great cost for developmentand eventual product yield is slower. A need has existed for a chargeplate with a high resolution that can be made inexpensively.

Thin film structures for charge plates have the advantage of extremelyhigh resolution (smaller line widths and spaces) and high yields. Thedisadvantage of fabricating a charge plate from thin film processes isthat the thin film technique has been unsuccessful in providing anelectrode structure that extends to the edge and over the charging faceof the charge plate.

The main difficulty in defining electrodes that continue from a topsurface to an edge surface lies in the difficulty of photo imaging thepattern. Typically, spun liquid photoresist tends to “ball up” along anedge giving rise to a thicker cross-sectional area. Since the amount ofphoto energy needed to expose the photoresist layer properly isdependent on the thickness of the photoresist layer, the balling upeffect causes unacceptable results because consistency cannot beassured.

Another difficulty with thin film processes arises is attempting toexpose a second surface after a first surface has already been exposed.Exposing the second surface has traditionally caused a detriment to thepreviously exposed material.

Other thin film techniques exist to form electrodes that “go around theedge.” For example, a shadow mask can be constructed out of wire or outof an L-shaped part with grooves and touch one side and edge to bepatterned. After the shadow mask is constructed, sputtering orevaporation of the remaining side can be patterned and etched.

Accordingly, a need exists for a technique that creates extremely highresolution (smaller line widths and spaces) and high product yields in acost effective manner.

The present embodiments described herein were designed to meet theseneeds.

SUMMARY OF THE INVENTION

The invention relates to a method for fabricating a charge plate for anink jet printhead, wherein the method includes the steps of removingportions of conductive material from a dimensionally stable substratewith a coating of conductive material using ablation to form at least afirst electrode and a second electrode on a first conductive face with afirst space between the first electrode and second electrode. Thedimensionally stable substrate with a coating of conductive material hasa first conductive edge between the first conductive face and aconductive charging face The method also includes the steps of removingportions of conductive material from the dimensionally stable substratewith a coating of conductive material to form a first electrodeextension which engages the first electrode on the conductive chargingface, and a second electrode extension which engages the secondelectrode on the conductive charging face. The first and secondelectrode extensions are electrically isolated from each other,additionally forming a first space between the electrode extensionswherein the first space connects with the first space between theelectrode extensions forming a charge plate.

The invention also relates to a charge plate for an ink jet printhead,which includes a first electrode and a second electrode on a first facewith a first space formed between the first and second electrodes on adimensionally stable non conductive substrate with a continuousconductive coating. The dimensionally stable non conductive substratewith a continuous conductive coating has a first edge between the firstface and a charging face. A first electrode extension on the chargingface engages the first electrode and a second electrode extension on thecharging face engages the second electrode. The first electrodeextension is electrically isolated from the second electrode extensionand the first space extends to separate the first and second electrodeextensions on the charging face.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiments presentedbelow, reference is made to the accompanying drawings, in which:

FIG. 1 depicts a top view of the substrate with four electrodes disposedon the first face;

FIG. 2 depicts a cross section of the substrate with the conductivecoating disposed on the charging face;

FIG. 3 depicts an isometric view of the substrate with electrodes formedon the first face and the charging face and the spaces and gaps;

FIG. 4 depicts a detailed cross section of a second embodiment of thefirst edge; and

FIG. 5 depicts an isometric view of the third side of the charging platemade according to one embodiment of the invention.

The present embodiments are detailed below with reference to the listedFigures.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining the present embodiments in detail, it is to beunderstood that the embodiments are not limited to the particulardescriptions and that it can be practiced or carried out in variousways.

The embodied methods and charge plate are subject to fewer electricalshortings between electrodes as compared to current conventionallyavailable charge plates. The methods provide techniques of manufacturewith fewer open circuits on the electrodes, thereby increasing thereliability of the charge plate for use in an ink jet printhead.

The methods herein were designed to provide techniques of manufacturewith fewer steps in order to produce usable charge plates that are morereliable than those formed by current methods. The charge plate is alsomore durable since electrical shorts will not easily pass through to theelectrodes created on the face and charge face of the resulting chargeplate.

The embodied methods permit a charge plate to be created with a sharpedge on the charge plate and electrodes that extend across the face andonto the charging face without gaps of currently commercializedtechniques, thereby improving printhead quality.

The embodied methods provide environmentally friendly manufacturingprocesses that do not require the use of large quantities of dangerouschemicals, which can poison the environment. The methods significantlycreate about half the chemical waste of current manufacturing methods,thereby reducing the amount waste that needs to be disposed of by makersof charge plates for ink jet printheads.

The methods of manufacturing charge plates as described herein are alsosafer for the employees of the manufacturing process since fewerflammable solvents are used in the process of laser ablation.

The embodied charge plates are more reliable than other systems sincethe resulting charge plates are less subject to degradation by inksbecause of the lack of gaps between the electrodes and the electrodeextensions. For that same reason, the charge plates provide a higherresistance to erosive chemicals and can be made much thinner thancurrent charge plates using the embodied methods.

The method for fabricating a charge plate for an ink jet printheadincludes the step of first removing portions of conductive material froma dimensionally stable dielectric substrate with a coating of conductivematerial using ablation to form at least a first electrode and a secondelectrode on a first conductive face with a first space between thefirst electrode and second electrode. The dimensionally stable substratewith a coating of conductive material has a first conductive edgebetween the first conductive face and a conductive charging face. Next,portions of conductive material are removed from the dimensionallystable dielectric substrate with a coating of conductive material toform a first electrode extension that engages the first electrode on theconductive charging face. A second electrode extension is formed inconjunction with the first electrode extension. The second electrodeextension engages the second electrode on the conductive charging face.The first and second electrode extensions are electrically isolated fromeach other. A first space is additionally formed between the electrodeextensions, wherein the first space connects with the first spacebetween the electrode extensions. The steps of removing the portions ofthe first face and the charging face can be completed simultaneously.

One or more additional spaces can be formed as each electrode is formedon both the charging face and the first top face of the substrate.

The dimensionally stable dielectric substrate typically is longer thanthe jet array for the ink jet printhead in order to better control thedrops from the ink jet printhead. In a preferred embodiment, thedimensionally stable dielectric substrate has a thin rectangular shapewith a coating of conductive material. The substrate typically has awidth between 1 inch and 6 inches, a length between ¼ inches and 30inches, and a thickness between 0.004 inch and 0.4 inches. The substratecan be composed of materials such as ceramic, glass, quartz, andcomposites thereof and combinations thereof.

In an alternative method, a second coating of conductive material can beadded on the substrate over a first coating of conductive coating ofconductive material. Each coating of conductive material typically has athickness between 1,000 Angstroms and 10,000 Angstroms. Examples ofusable coatings are titanium, gold, platinum, palladium, silver, nickel,tantalum, tungsten alloys, and combinations thereof.

The formed charge plate with electrodes can be coated with a protectivedielectric material. Example types of protective dielectric materialsinclude epoxies, polyimides, thick films, thin films, and combinationsof these. The films are described below in more detail. The protectivedielectric materials can be deposited by screen printing, vapordeposition, chemical deposition, sputtering, or combinations thereof.Portions of the protective dielectric material can be removed from thesubstrate by laser ablation.

In an alternative to the above methods, a first third face electrode anda second third face electrode can be formed on a third face of thesubstrate with a fourth space between the first third face electrode andthe second third face electrode. A third edge can exist between thethird face and the charging face. A non patterned conductive region canbe formed between the fourth space and the third edge. A first thirdface electrode extension can be formed to engage the first third faceelectrode. A second third face electrode extension can be made in amanner similar to the initial electrode extensions where the electrodeextensions engage the respective electrode. The electrode extensions areformed by removing a portion of the continuous conductive coatingdeposited on the charging face. In conjunction with the electrodeextensions, a space is formed on the charging face between the at leasttwo third face electrode extensions. The first third face electrodeextension is then electrically isolated from the second third faceelectrode extension. A portion of the first third face electrode and thesecond third face electrode can be removed to extend the fourth space toform a continuous connected space with a fifth space on the chargingface.

These methods are contemplated to be usable for both continuous ink jetprinthead and drop on demand printheads.

The charge plate is formed by the steps of the embodied methods.

Referring now to the figures, FIG. 1 depicts a top view of the chargeplate having a first and second electrode 27 and 28 on a first face 10of a dimensionally stable dielectric substrate with a continuousconductive coating. A first space 31 is created between the firstelectrode 27 and second electrode 28 by removing, such as by ablating, aportion of the continuous conductive coating. A second space 32 iscreated between the second electrode 28 and a third electrode 29. Athird space 33 is created between the third electrode 29 and a fourthelectrode 30. The additional electrodes 28, 29, and 30 are formed bylaser ablating or otherwise removing portions of the continuousconductive coating from the substrate.

The first face 10 has a first edge 17. The first edge 17 is preferably asharp edge sharp, or when coated with the continuous conductive coating,can be beveled. If the first edge 17 is beveled, the first edge 17typically has a radius of less than 50 microns.

FIG. 1 further depicts a non-patterned conductive region 34 formedbetween the first space 31 and the first edge 17. The first space 31extends from the first edge 17 to all additional electrodes formed onthe first face 10.

FIG. 2 examples a cross sectional view of the dimensionally stabledielectric substrate 9 with a continuous conductive coating 26. Thecontinuous conductive coating 26 can be a single metal, a first metal onanother metal, a conductive layer of a material other than metal ormetal alloy, or two or more different conductive layers. The first edge17 is shown between the first face 10 and a charging face 12. Titaniumcan be used as a metal with the dual layer conductive coatingembodiment. Gold, platinum, palladium, silver, nickel, tantalum,tungsten alloys, or combinations thereof can also be used.

FIG. 3 depicts a side view showing the electrodes and electrodeextensions that form the charging plate according to the embodiedmethods. A first electrode 27 and second electrode 28 are formed on thetop face 10 of the substrate with a first space 31 is formed between theelectrodes. A second space 32 is created between the second electrode 28and a third electrode 29. A third space 33 is created between the thirdelectrode 29 and a fourth electrode 30. In the embodiment depicted inFIG. 3, the electrodes extend all the way to first edge 17. The firstelectrode extension 40 on the charging face engages the first electrode27 and the second electrode extension 41 engages the second electrode28. Similarly, FIG. 3 shows that third electrode 29 engages a thirdelectrode extension 42 and the fourth electrode 30 engages a fourthelectrode extension 43. Any number of electrodes and connected electrodeextensions can be formed by these methods.

The spaces formed between the electrodes can be created by removingconductive coating material from the substrate.

Any known method of removing conductive coating material from asubstrate can be used, but ablation is the preferred technique. Ablationcan be performed using a laser or an electron beam. Ablation can formthe spaces, not only between the electrodes on the first side 10, but onthe charging face 12 between the electrode extensions.

Continuing with FIG. 3, the first electrode extension 40 is electricallyisolated from the second electrode extension 41 with a space 44. Thethird electrode extension 42 is similarly separated from the secondelectrode extension 41 by a space 45. The third electrode extension 42is separated from the fourth electrode extension by another space 46.

FIG. 4 shows the substrate 9 with the continuous conductive coating 26to form the charging plate 39. The top side 10 has a protectivedielectric coating 52 disposed over the conductive coating, while theprotective dielectric coating 52 does not cover the coating used to formthe charging face 12. The protective dielectric material 52 can be anepoxy, such as Epotek 353ND from Epotek Technology of Billerica, Mass.;a polyimide, such as Kapton™ from DuPont of Wilmington, Del.; a thickfilm, such as the 5704 dielectric film from DuPont of Wilmington, Del.;or a thin film, such as silicon nitride, silicon carbide, aluminumoxide, or parylene from Union Carbide of Danbury, Conn. The protectivedielectric material 52 can be a combination of these materials. Theprotective dielectric material 52 can be deposited by screen printing,vapor deposition, chemical deposition, sputtering, or combinations ofthese techniques.

FIG. 5 depicts an isometric bottom view of an embodiment of the chargingplate 39. In the embodiment depicted, the device includes a first thirdface electrode 53 and a second third face electrode 54 formed on a thirdface 59. A fourth space 60 is between the first third face electrode 53and the second third face electrode 54. A conductive region is betweenthe fourth space 60 and the third edge 19. Additional electrodes areformed by removing portions of the conductive coating as described inthe embodied methods. A first third face electrode extension 56 isformed where the first third face electrode extension 56 engages thefirst third face electrode 53. A second third face electrode extension57 engages the second third face electrode 54. A third third faceelectrode extension 58 engages the third third face electrode 55. Afifth space 68 on the charging face is between the third face electrodeextensions 54 and 57. The first third face electrode extension 57 iselectrically isolated from the second third face electrode extension 54.A fourth space 60 forms a continuous connected space with the fifthspace 68 on the charging face.

The electrodes of the top face and the third face can have analternative arrangement so that the corresponding electrode extensionsalternate on the charging face. In another embodiment, the electrodesand corresponding electrode extensions can be grouped in alternatinggroups of electrodes, such as three electrodes and electrode extensionson the charging face from the top side and the three electrodes andelectrode extensions onto the charging face form the third side.

The embodiments have been described in detail with particular referenceto certain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the scope of theembodiments, especially to those skilled in the art.

PARTS LIST

-   9 dimensionally stable dielectric substrate-   10 first face-   12 charging face-   17 first edge-   19 third edge-   26 continuous conductive coating-   27 first electrode-   28 second electrode-   29 third electrode-   30 fourth electrode-   31 first space-   32 second space-   33 third space-   34 non patterned conductive region-   39 charge plate-   40 first electrode extension-   41 second electrode extension-   42 third electrode extension-   43 fourth electrode extension-   44 first space on the charging face-   45 second space on the charging face-   46 third space on the charging face-   47 second gap-   52 protective dielectric material-   53 first third face electrode-   54 second third face electrode-   55 third third face electrode-   56 first third face electrode extension-   57 second third face electrode extension-   58 third third face electrode extension-   59 third face-   60 fourth space-   68 fifth space

1. A method for fabricating a charge plate for an ink jet printhead,wherein the method comprises the steps of: a. removing portions ofconductive material from a dimensionally stable dielectric substratewith a coating of conductive material using ablation to form at least afirst electrode and a second electrode on a first conductive face with afirst space between the first electrode and second electrode, andwherein said the dimensionally stable substrate with a coating ofconductive material has a first conductive edge between the firstconductive face and a conductive charging face; and b. removing portionsof conductive material from the dimensionally stable dielectricsubstrate with a coating of conductive material to form a firstelectrode extension which engages the first electrode on the conductivecharging face, and a second electrode extension which engages the secondelectrode on the conductive charging face and wherein the first andsecond electrode extensions are electrically isolated from each other,additionally forming a first space between the electrode extensionswherein the first space connects with the first space between theelectrode extensions.
 2. The method of claim 1, further comprising thestep of c. forming a first third face electrode and a second third faceelectrode on a third face with a fourth space between the first thirdface electrode and the second third face electrode on the dimensionallystable dielectric substrate and forming a third edge between the thirdface and the charging face by removing a portion of the conductivecoating deposited on the third side forming a fourth space, and whereina non patterned conductive region is formed between the fourth space andthe third edge; d. forming on the charging face a first third faceelectrode extension which engages the first third face electrode and asecond third face electrode extension which engages the second thirdface electrode by removing a portion of the continuous conductivecoating deposited on the charging face to form a fifth space on thecharging face between the at least two third face electrode extensions,and wherein the first third face electrode extension is electricallyisolated from the second third face electrode extension; and e. removinga portion of the first third face electrode and the second third faceelectrode to extend the fourth space to form a continuous connectedspace with fifth space on the charging face.
 3. The method of claim 1,further comprising the step of forming at least one additional space asat least one additional electrode is formed on both faces.
 4. The methodof claim 1, further comprising the step of coating the charge plate withelectrodes and electrode extension formed thereon with a protectivedielectric material.
 5. The method of claim 4, wherein the protectivedielectric material is a member of the group: an epoxy, a polyimide, athick film, a thin film and combinations thereof.
 6. The method of claim4, wherein the protective dielectric material can be deposited by screenprinting, vapor deposition, chemical deposition, sputtering, orcombinations thereof.
 7. The method of claim 1 wherein the steps forremoving the portions of the first face and the charging face aresimultaneously performed.
 8. The method of claim 1, wherein the step forremoving portions of conductive material from a dimensionally stabledielectric substrate with a coating of conductive material is performedby laser ablation.
 9. The method of claim 1, further comprising using adimensionally stable dielectric substrate which has a length that isslightly longer than the length of a jet array for the ink jetprinthead.
 10. The method of claim 1, wherein the ink jet printhead isfor a continuous ink jet printhead.
 11. The method of claim 1, whereinthe dimensionally stable dielectric substrate with a coating ofconductive material has a thin rectangular shape.
 12. The method ofclaim 1, wherein the dimensionally stable dielectric substrate with acoating of conductive material has a width between 1 inch and 6 inches,a length between ¼ inches and 30 inches, and a thickness between 0.004inch and 0.4 inch.
 13. The method of claim 1, wherein the dimensionallystable dielectric substrate with a coating of conductive materialcomprises a coating with at least a second conductive coating depositedover a first conductive coating.
 14. The method of claim 1, wherein thedimensionally stable dielectric substrate with a coating of conductivematerial is a ceramic, glass, quartz, and composites thereof.
 15. Themethod of claim 1, wherein the dimensionally stable dielectric substratewith a coating of conductive material comprises a coating with athickness between 1,000 Angstroms and 10,000 Angstroms.
 16. The methodof claim 1, wherein the dimensionally stable dielectric substrate with acoating of conductive material comprises a coating of titanium, gold,platinum, palladium, silver, nickel, tantalum, tungsten alloys, andcombinations thereof.
 17. The method of claim 1, wherein the first edgeis beveled.
 18. The method of claim 17, wherein the first edge has aradius of less than 50 microns.
 19. A charge plate for an ink jetprinthead made by the method of claim
 1. 20. The device of claim 19,wherein the first space integrally connects with additional continuousconnected spaces on the charging face formed from the removal of aportion of the additional electrode.
 21. The device of claim 19, whereinthe dimensionally stable dielectric substrate has a length that isslightly longer than the length of a jet array for the ink jetprinthead.
 22. The device of claim 18, wherein the dimensionally stabledielectric substrate is a thin rectangular shape
 23. The device of claim19, wherein the dimensionally stable dielectric substrate has a widthbetween 1 inch and 6 inches, a length between ¼ inches and 30 inches,and a thickness between 0.004 inch and 0.4 inch.
 24. The device of claim19, wherein the dimensionally stable dielectric substrate is a ceramic,glass, quartz, composites thereof and combinations thereof.
 25. Thedevice of claim 19, wherein the continuous conductive coating is between1,000 Angstroms and 10,000 Angstroms.
 26. The device of claim 19,wherein the continuous conductive coating is titanium, gold, platinum,palladium, silver, nickel, tantalum, tungsten alloys, and combinationsthereof.
 27. The device of claim 19, wherein the first edge is a bevelededge.
 28. The device of claim 27, wherein the first edge has a radius ofless than 50 microns.
 29. The device of claim 19, further comprising aprotective dielectric material disposed over the electrodes on the firstface.
 30. The device of claim 29, wherein the protective dielectricmaterial is a member of the group: an epoxy, a polyimide, a thick film,a thin film or combinations thereof.
 31. The device of claim 19, furthercomprising the steps of: f. first third face electrode and a secondthird face electrode formed on a third face with a fourth space betweenthe first third face electrode and the second third face electrode and athird edge between the third face and the charging face, a non patternedconductive region is between the fourth space and the third edge; g. afirst third face electrode extension which engages the first third faceelectrode and a second third face electrode extension which engages thesecond third face electrode, and a fifth space on the charging facebetween the third face electrode extensions, and wherein the first thirdface electrode extension is electrically isolated from the second thirdface electrode extension, and a fourth space forms a continuousconnected space with the fifth space on the charging face.